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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 8 |
| 3 | 6 |
| 4 | 104 |
| 5 | 553 |
| 6 | 2232 |
| 7 | 21312 |
| 8 | 86812 |
| 9 | 553861 |
| 10 | 3407800 |
| 11 | 16888371 |
| 12 | 108293432 |
| 13 | 590867753 |
| 14 | 3371103500 |
| 15 | 19838294637 |
| 16 | 109788155032 |
| 17 | 640910245323 |
| 18 | 3646664185104 |
| 19 | 20751408860377 |
| 20 | 119635268746040 |
| 21 | 679631607840939 |
[0,8,6,104,553,2232,21312,86812,553861,3407800, 16888371,108293432,590867753,3371103500, 19838294637,109788155032,640910245323, 3646664185104,20751408860377,119635268746040, 679631607840939] |